Not to be outdone, Democrats in the House of Representatives launched an Affordable Drug Pricing Task Force to address the issue. In a letter sent Wednesday to Oversight and Government Reform Committee chairman US Rep. Jason Chaffetz (R-UT), committee Democrats called on him to hold a hearing on Valeant and Turing later this month.

So what’s the goal of all these Congressional task forces, investigations and letters? Getting a more transparent account of what goes into a drug’s wholesale price, especially when it rises faster than the rate of inflation.

But the drug companies won’t be quick to give up that information, even if they say they will cooperate with the Senate’s investigation and whatever the House can cook up.

A record of cagey responses

Already, Valeant, run by J. Michael Pearson, and Turing, run by Martin Shkreli, have rebuffed requests for information on how they set their prices

Among the drugs Sanders and Cummings requested information about were Nitropress and Isuprel, two heart drugs that have shot up in price in recent years.

Similarly, Turing said it is “unable to provide certain numbers and data related to proprietary information,” in response to a similar letter about the drastic increase of Daraprim, a 62-year-old drug that’s used to treat malaria and parasitic infections in patients with weakened immune systems.

The Senate’s probe

The Senate will hold its hearing on drug prices on Dec. 9.

When we asked Turing CEO Martin Shkreli about the Senate investigation earlier this week, he said he wasn’t convinced he’d have to attend the hearing at all.

“When my lawyers tell me I absolutely have to go, I’ll go,” he said. “They don’t have subpoena power until they have got widespread support. I don’t have to go to a hearing unless there’s widespread support.”

And here’s what his company, Turing Pharmaceuticals, sent Business Insider in regards to the Senate’s letter:

“We are reviewing the Committee’s request and, as we have and continue to do with similar congressional inquiries, we look forward to having an open and honest dialogue about drug pricing.”

Valeant’s Little issued a similarly cagey response, saying “the prices of individual drugs fluctuate due to a number of factors.”

Two other drug companies who received Senate letters appear to be responding, if only partially: